Reduce compression memory use with map[string]uint16 (#852)

* Reduce compression memory use with map[string]uint16

map[string]uint16 uses 25% less memory per-entry than a map[string]int
(16+2)/(16+8) = 0.75. All entries in the compression map are bound by
maxCompressionOffset which is 14-bits and fits within a uint16.

* Add PackMsg benchmark with more RRs

* Add a comment to the compressionMap struct

defaults.go

@@ -166,7 +166,7 @@ func (dns *Msg) IsEdns0() *OPT {
 // label fits in 63 characters, but there is no length check for the entire
 // string s. I.e.  a domain name longer than 255 characters is considered valid.
 func IsDomainName(s string) (labels int, ok bool) {
-	_, labels, err := packDomainName(s, nil, 0, nil, false)
+	_, labels, err := packDomainName(s, nil, 0, compressionMap{}, false)
 	return labels, err == nil
 }
 

dns.go

@@ -42,7 +42,7 @@ type RR interface {
 	len(off int, compression map[string]struct{}) int
 
 	// pack packs an RR into wire format.
-	pack([]byte, int, map[string]int, bool) (int, error)
+	pack([]byte, int, compressionMap, bool) (int, error)
 }
 
 // RR_Header is the header all DNS resource records share.

dns_bench_test.go

@@ -277,6 +277,33 @@ func BenchmarkPackMsg(b *testing.B) {
 	}
 }
 
+func BenchmarkPackMsgMassive(b *testing.B) {
+	makeMsg := func(question string, ans, ns, e []RR) *Msg {
+		msg := new(Msg)
+		msg.SetQuestion(Fqdn(question), TypeANY)
+		msg.Answer = append(msg.Answer, ans...)
+		msg.Ns = append(msg.Ns, ns...)
+		msg.Extra = append(msg.Extra, e...)
+		msg.Compress = true
+		return msg
+	}
+	const name1 = "12345678901234567890123456789012345.12345678.123."
+	rrMx := testRR(name1 + " 3600 IN MX 10 " + name1)
+	answer := []RR{rrMx, rrMx}
+	for i := 0; i < 128; i++ {
+		rrA := testRR(fmt.Sprintf("example%03d.something%03delse.org. 2311 IN A 127.0.0.1", i/32, i%32))
+		answer = append(answer, rrA)
+	}
+	answer = append(answer, rrMx, rrMx)
+	msg := makeMsg(name1, answer, nil, nil)
+	buf := make([]byte, 512)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _ = msg.PackBuffer(buf)
+	}
+}
+
 func BenchmarkPackMsgOnlyQuestion(b *testing.B) {
 	msg := new(Msg)
 	msg.SetQuestion(Fqdn("12345678901234567890123456789012345.12345678.123."), TypeANY)

length_test.go

@@ -326,7 +326,7 @@ func TestCompareCompressionMapsForANY(t *testing.T) {
 		lenFake := msgLenWithCompressionMap(msg, compressionFake)
 
 		compressionReal := make(map[string]int)
-		buf, err := msg.packBufferWithCompressionMap(nil, compressionReal, true)
+		buf, err := msg.packBufferWithCompressionMap(nil, compressionMap{ext: compressionReal}, true)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -359,7 +359,7 @@ func TestCompareCompressionMapsForSRV(t *testing.T) {
 		lenFake := msgLenWithCompressionMap(msg, compressionFake)
 
 		compressionReal := make(map[string]int)
-		buf, err := msg.packBufferWithCompressionMap(nil, compressionReal, true)
+		buf, err := msg.packBufferWithCompressionMap(nil, compressionMap{ext: compressionReal}, true)
 		if err != nil {
 			t.Fatal(err)
 		}

msg.go

@@ -190,6 +190,39 @@ var RcodeToString = map[int]string{
 	RcodeBadCookie: "BADCOOKIE",
 }
 
+// compressionMap is used to allow a more efficient compression map
+// to be used for internal packDomainName calls without changing the
+// signature or functionality of public API.
+//
+// In particular, map[string]uint16 uses 25% less per-entry memory
+// than does map[string]int.
+type compressionMap struct {
+	ext map[string]int    // external callers
+	int map[string]uint16 // internal callers
+}
+
+func (m compressionMap) valid() bool {
+	return m.int != nil || m.ext != nil
+}
+
+func (m compressionMap) insert(s string, pos int) {
+	if m.ext != nil {
+		m.ext[s] = pos
+	} else {
+		m.int[s] = uint16(pos)
+	}
+}
+
+func (m compressionMap) find(s string) (int, bool) {
+	if m.ext != nil {
+		pos, ok := m.ext[s]
+		return pos, ok
+	}
+
+	pos, ok := m.int[s]
+	return int(pos), ok
+}
+
 // Domain names are a sequence of counted strings
 // split at the dots. They end with a zero-length string.
 
@@ -198,11 +231,11 @@ var RcodeToString = map[int]string{
 // map needs to hold a mapping between domain names and offsets
 // pointing into msg.
 func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
-	off1, _, err = packDomainName(s, msg, off, compression, compress)
+	off1, _, err = packDomainName(s, msg, off, compressionMap{ext: compression}, compress)
 	return
 }
 
-func packDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, labels int, err error) {
+func packDomainName(s string, msg []byte, off int, compression compressionMap, compress bool) (off1 int, labels int, err error) {
 	// special case if msg == nil
 	lenmsg := 256
 	if msg != nil {
@@ -292,8 +325,8 @@ loop:
 			// Don't try to compress '.'
 			// We should only compress when compress is true, but we should also still pick
 			// up names that can be used for *future* compression(s).
-			if compression != nil && !isRootLabel(s, bs, begin, ls) {
-				if p, ok := compression[s[compBegin:]]; ok {
+			if compression.valid() && !isRootLabel(s, bs, begin, ls) {
+				if p, ok := compression.find(s[compBegin:]); ok {
 					// The first hit is the longest matching dname
 					// keep the pointer offset we get back and store
 					// the offset of the current name, because that's
@@ -306,7 +339,7 @@ loop:
 					}
 				} else if off < maxCompressionOffset {
 					// Only offsets smaller than maxCompressionOffset can be used.
-					compression[s[compBegin:]] = off
+					compression.insert(s[compBegin:], off)
 				}
 			}
 
@@ -586,6 +619,10 @@ func intToBytes(i *big.Int, length int) []byte {
 // PackRR packs a resource record rr into msg[off:].
 // See PackDomainName for documentation about the compression.
 func PackRR(rr RR, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
+	return packRR(rr, msg, off, compressionMap{ext: compression}, compress)
+}
+
+func packRR(rr RR, msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
 	if rr == nil {
 		return len(msg), &Error{err: "nil rr"}
 	}
@@ -708,15 +745,15 @@ func (dns *Msg) PackBuffer(buf []byte) (msg []byte, err error) {
 	// If this message can't be compressed, avoid filling the
 	// compression map and creating garbage.
 	if dns.Compress && dns.isCompressible() {
-		compression := make(map[string]int) // Compression pointer mappings.
-		return dns.packBufferWithCompressionMap(buf, compression, true)
+		compression := make(map[string]uint16) // Compression pointer mappings.
+		return dns.packBufferWithCompressionMap(buf, compressionMap{int: compression}, true)
 	}
 
-	return dns.packBufferWithCompressionMap(buf, nil, false)
+	return dns.packBufferWithCompressionMap(buf, compressionMap{}, false)
 }
 
 // packBufferWithCompressionMap packs a Msg, using the given buffer buf.
-func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression map[string]int, compress bool) (msg []byte, err error) {
+func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression compressionMap, compress bool) (msg []byte, err error) {
 	if dns.Rcode < 0 || dns.Rcode > 0xFFF {
 		return nil, ErrRcode
 	}
@@ -784,19 +821,19 @@ func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression map[string]
 		}
 	}
 	for _, r := range dns.Answer {
-		off, err = PackRR(r, msg, off, compression, compress)
+		off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
 	}
 	for _, r := range dns.Ns {
-		off, err = PackRR(r, msg, off, compression, compress)
+		off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
 	}
 	for _, r := range dns.Extra {
-		off, err = PackRR(r, msg, off, compression, compress)
+		off, err = packRR(r, msg, off, compression, compress)
 		if err != nil {
 			return nil, err
 		}
@@ -1072,8 +1109,8 @@ func (dns *Msg) CopyTo(r1 *Msg) *Msg {
 	return r1
 }
 
-func (q *Question) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
-	off, err := PackDomainName(q.Name, msg, off, compression, compress)
+func (q *Question) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
+	off, _, err := packDomainName(q.Name, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -1114,7 +1151,7 @@ func unpackQuestion(msg []byte, off int) (Question, int, error) {
 	return q, off, err
 }
 
-func (dh *Header) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (dh *Header) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := packUint16(dh.Id, msg, off)
 	if err != nil {
 		return off, err

msg_generate.go

@@ -80,7 +80,7 @@ func main() {
 		o := scope.Lookup(name)
 		st, _ := getTypeStruct(o.Type(), scope)
 
-		fmt.Fprintf(b, "func (rr *%s) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {\n", name)
+		fmt.Fprintf(b, "func (rr *%s) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {\n", name)
 		fmt.Fprint(b, `off, err := rr.Hdr.pack(msg, off, compression, compress)
 if err != nil {
 	return off, err
@@ -116,9 +116,9 @@ return off, err
 			switch {
 			case st.Tag(i) == `dns:"-"`: // ignored
 			case st.Tag(i) == `dns:"cdomain-name"`:
-				o("off, err = PackDomainName(rr.%s, msg, off, compression, compress)\n")
+				o("off, _, err = packDomainName(rr.%s, msg, off, compression, compress)\n")
 			case st.Tag(i) == `dns:"domain-name"`:
-				o("off, err = PackDomainName(rr.%s, msg, off, compression, false)\n")
+				o("off, _, err = packDomainName(rr.%s, msg, off, compression, false)\n")
 			case st.Tag(i) == `dns:"a"`:
 				o("off, err = packDataA(rr.%s, msg, off)\n")
 			case st.Tag(i) == `dns:"aaaa"`:

msg_helpers.go

@@ -101,12 +101,12 @@ func unpackHeader(msg []byte, off int) (rr RR_Header, off1 int, truncmsg []byte,
 
 // pack packs an RR header, returning the offset to the end of the header.
 // See PackDomainName for documentation about the compression.
-func (hdr RR_Header) pack(msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
+func (hdr RR_Header) pack(msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
 	if off == len(msg) {
 		return off, nil
 	}
 
-	off, err = PackDomainName(hdr.Name, msg, off, compression, compress)
+	off, _, err = packDomainName(hdr.Name, msg, off, compression, compress)
 	if err != nil {
 		return len(msg), err
 	}
@@ -621,10 +621,10 @@ func unpackDataDomainNames(msg []byte, off, end int) ([]string, int, error) {
 	return servers, off, nil
 }
 
-func packDataDomainNames(names []string, msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func packDataDomainNames(names []string, msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	var err error
 	for j := 0; j < len(names); j++ {
-		off, err = PackDomainName(names[j], msg, off, compression, compress)
+		off, _, err = packDomainName(names[j], msg, off, compression, compress)
 		if err != nil {
 			return len(msg), err
 		}

privaterr.go

@@ -69,7 +69,7 @@ func (r *PrivateRR) copy() RR {
 	}
 	return rr
 }
-func (r *PrivateRR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (r *PrivateRR) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := r.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err

zmsg.go

@@ -4,7 +4,7 @@ package dns
 
 // pack*() functions
 
-func (rr *A) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *A) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -18,7 +18,7 @@ func (rr *A) pack(msg []byte, off int, compression map[string]int, compress bool
 	return off, nil
 }
 
-func (rr *AAAA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *AAAA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -32,7 +32,7 @@ func (rr *AAAA) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *AFSDB) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *AFSDB) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -42,7 +42,7 @@ func (rr *AFSDB) pack(msg []byte, off int, compression map[string]int, compress
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Hostname, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Hostname, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -50,7 +50,7 @@ func (rr *AFSDB) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *ANY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *ANY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -60,7 +60,7 @@ func (rr *ANY) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *AVC) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *AVC) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -74,7 +74,7 @@ func (rr *AVC) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *CAA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CAA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -96,7 +96,7 @@ func (rr *CAA) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *CDNSKEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CDNSKEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -122,7 +122,7 @@ func (rr *CDNSKEY) pack(msg []byte, off int, compression map[string]int, compres
 	return off, nil
 }
 
-func (rr *CDS) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CDS) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -148,7 +148,7 @@ func (rr *CDS) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *CERT) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CERT) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -174,13 +174,13 @@ func (rr *CERT) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *CNAME) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CNAME) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Target, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Target, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -188,7 +188,7 @@ func (rr *CNAME) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *CSYNC) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *CSYNC) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -210,7 +210,7 @@ func (rr *CSYNC) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *DHCID) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *DHCID) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -224,7 +224,7 @@ func (rr *DHCID) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *DLV) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *DLV) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -250,13 +250,13 @@ func (rr *DLV) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *DNAME) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *DNAME) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Target, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Target, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -264,7 +264,7 @@ func (rr *DNAME) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *DNSKEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *DNSKEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -290,7 +290,7 @@ func (rr *DNSKEY) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *DS) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *DS) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -316,7 +316,7 @@ func (rr *DS) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *EID) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *EID) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -330,7 +330,7 @@ func (rr *EID) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *EUI48) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *EUI48) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -344,7 +344,7 @@ func (rr *EUI48) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *EUI64) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *EUI64) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -358,7 +358,7 @@ func (rr *EUI64) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *GID) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *GID) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -372,7 +372,7 @@ func (rr *GID) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *GPOS) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *GPOS) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -394,7 +394,7 @@ func (rr *GPOS) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *HINFO) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *HINFO) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -412,7 +412,7 @@ func (rr *HINFO) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *HIP) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *HIP) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -446,7 +446,7 @@ func (rr *HIP) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *KEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *KEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -472,7 +472,7 @@ func (rr *KEY) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *KX) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *KX) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -482,7 +482,7 @@ func (rr *KX) pack(msg []byte, off int, compression map[string]int, compress boo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Exchanger, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Exchanger, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -490,7 +490,7 @@ func (rr *KX) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *L32) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *L32) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -508,7 +508,7 @@ func (rr *L32) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *L64) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *L64) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -526,7 +526,7 @@ func (rr *L64) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *LOC) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *LOC) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -564,7 +564,7 @@ func (rr *LOC) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *LP) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *LP) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -574,7 +574,7 @@ func (rr *LP) pack(msg []byte, off int, compression map[string]int, compress boo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Fqdn, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Fqdn, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -582,13 +582,13 @@ func (rr *LP) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MB) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MB) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Mb, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mb, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -596,13 +596,13 @@ func (rr *MB) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MD) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MD) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Md, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Md, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -610,13 +610,13 @@ func (rr *MD) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MF) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MF) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Mf, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mf, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -624,13 +624,13 @@ func (rr *MF) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MG) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MG) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Mg, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mg, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -638,17 +638,17 @@ func (rr *MG) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MINFO) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MINFO) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Rmail, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Rmail, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Email, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Email, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -656,13 +656,13 @@ func (rr *MINFO) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *MR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MR) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Mr, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mr, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -670,7 +670,7 @@ func (rr *MR) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *MX) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *MX) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -680,7 +680,7 @@ func (rr *MX) pack(msg []byte, off int, compression map[string]int, compress boo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Mx, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mx, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -688,7 +688,7 @@ func (rr *MX) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *NAPTR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NAPTR) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -714,7 +714,7 @@ func (rr *NAPTR) pack(msg []byte, off int, compression map[string]int, compress
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Replacement, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Replacement, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -722,7 +722,7 @@ func (rr *NAPTR) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *NID) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NID) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -740,7 +740,7 @@ func (rr *NID) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *NIMLOC) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NIMLOC) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -754,7 +754,7 @@ func (rr *NIMLOC) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *NINFO) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NINFO) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -768,13 +768,13 @@ func (rr *NINFO) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *NS) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NS) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Ns, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Ns, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -782,13 +782,13 @@ func (rr *NS) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *NSAPPTR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NSAPPTR) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Ptr, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Ptr, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -796,13 +796,13 @@ func (rr *NSAPPTR) pack(msg []byte, off int, compression map[string]int, compres
 	return off, nil
 }
 
-func (rr *NSEC) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NSEC) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.NextDomain, msg, off, compression, false)
+	off, _, err = packDomainName(rr.NextDomain, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -814,7 +814,7 @@ func (rr *NSEC) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *NSEC3) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NSEC3) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -859,7 +859,7 @@ func (rr *NSEC3) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *NSEC3PARAM) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *NSEC3PARAM) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -892,7 +892,7 @@ func (rr *NSEC3PARAM) pack(msg []byte, off int, compression map[string]int, comp
 	return off, nil
 }
 
-func (rr *OPENPGPKEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *OPENPGPKEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -906,7 +906,7 @@ func (rr *OPENPGPKEY) pack(msg []byte, off int, compression map[string]int, comp
 	return off, nil
 }
 
-func (rr *OPT) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *OPT) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -920,13 +920,13 @@ func (rr *OPT) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *PTR) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *PTR) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Ptr, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Ptr, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -934,7 +934,7 @@ func (rr *PTR) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *PX) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *PX) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -944,11 +944,11 @@ func (rr *PX) pack(msg []byte, off int, compression map[string]int, compress boo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Map822, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Map822, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Mapx400, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Mapx400, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -956,7 +956,7 @@ func (rr *PX) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *RFC3597) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *RFC3597) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -970,7 +970,7 @@ func (rr *RFC3597) pack(msg []byte, off int, compression map[string]int, compres
 	return off, nil
 }
 
-func (rr *RKEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *RKEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -996,17 +996,17 @@ func (rr *RKEY) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *RP) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *RP) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Mbox, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Mbox, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Txt, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Txt, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1014,7 +1014,7 @@ func (rr *RP) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *RRSIG) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *RRSIG) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1048,7 +1048,7 @@ func (rr *RRSIG) pack(msg []byte, off int, compression map[string]int, compress
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.SignerName, msg, off, compression, false)
+	off, _, err = packDomainName(rr.SignerName, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1060,7 +1060,7 @@ func (rr *RRSIG) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *RT) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *RT) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1070,7 +1070,7 @@ func (rr *RT) pack(msg []byte, off int, compression map[string]int, compress boo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Host, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Host, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1078,7 +1078,7 @@ func (rr *RT) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *SIG) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SIG) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1112,7 +1112,7 @@ func (rr *SIG) pack(msg []byte, off int, compression map[string]int, compress bo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.SignerName, msg, off, compression, false)
+	off, _, err = packDomainName(rr.SignerName, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1124,7 +1124,7 @@ func (rr *SIG) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *SMIMEA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SMIMEA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1150,17 +1150,17 @@ func (rr *SMIMEA) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *SOA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SOA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Ns, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Ns, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Mbox, msg, off, compression, compress)
+	off, _, err = packDomainName(rr.Mbox, msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
@@ -1188,7 +1188,7 @@ func (rr *SOA) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *SPF) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SPF) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1202,7 +1202,7 @@ func (rr *SPF) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *SRV) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SRV) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1220,7 +1220,7 @@ func (rr *SRV) pack(msg []byte, off int, compression map[string]int, compress bo
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.Target, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Target, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1228,7 +1228,7 @@ func (rr *SRV) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *SSHFP) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *SSHFP) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1250,7 +1250,7 @@ func (rr *SSHFP) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *TA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1276,17 +1276,17 @@ func (rr *TA) pack(msg []byte, off int, compression map[string]int, compress boo
 	return off, nil
 }
 
-func (rr *TALINK) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TALINK) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.PreviousName, msg, off, compression, false)
+	off, _, err = packDomainName(rr.PreviousName, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
-	off, err = PackDomainName(rr.NextName, msg, off, compression, false)
+	off, _, err = packDomainName(rr.NextName, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1294,13 +1294,13 @@ func (rr *TALINK) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *TKEY) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TKEY) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Algorithm, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Algorithm, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1340,7 +1340,7 @@ func (rr *TKEY) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *TLSA) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TLSA) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1366,13 +1366,13 @@ func (rr *TLSA) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *TSIG) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TSIG) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
 	}
 	headerEnd := off
-	off, err = PackDomainName(rr.Algorithm, msg, off, compression, false)
+	off, _, err = packDomainName(rr.Algorithm, msg, off, compression, false)
 	if err != nil {
 		return off, err
 	}
@@ -1412,7 +1412,7 @@ func (rr *TSIG) pack(msg []byte, off int, compression map[string]int, compress b
 	return off, nil
 }
 
-func (rr *TXT) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *TXT) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1426,7 +1426,7 @@ func (rr *TXT) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *UID) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *UID) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1440,7 +1440,7 @@ func (rr *UID) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *UINFO) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *UINFO) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1454,7 +1454,7 @@ func (rr *UINFO) pack(msg []byte, off int, compression map[string]int, compress
 	return off, nil
 }
 
-func (rr *URI) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *URI) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err
@@ -1476,7 +1476,7 @@ func (rr *URI) pack(msg []byte, off int, compression map[string]int, compress bo
 	return off, nil
 }
 
-func (rr *X25) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {
+func (rr *X25) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
 	off, err := rr.Hdr.pack(msg, off, compression, compress)
 	if err != nil {
 		return off, err